Early Mistreatment Contributes to Social Behavior Disorders in Zebrafish

Abstract

Adverse experiences during childhood have been the focus of a series of studies due to the psychological damage observed in individuals who suffered abuse during their youth. Studies with model animals that can mimic these observations can significantly contribute to understanding the mechanisms behind this phenomenon. In our experiments, young zebrafish (20 dpf) were exposed to aggressive alcoholized male adults for 30 min for 10 days. At 30 dpf, the animals were tested for shoal formation, and at 60 dpf, locomotion and aggression were evaluated. Animals that suffered oppression from adults showed greater group cohesion and lower attack emission and higher distance from the image in the mirror test. Locomotor parameters were not changed. These results show that the stress caused by aggression exposure in the juvenile phase led to increased fear and avoidance behavior later in life. Moreover, we confirm the importance of the zebrafish as a sensitive tool for studies on the effects of early mistreatment and its consequences to adult behavior.

Teleosts as behaviour test models for social stress

“…Furthermore, using multiple types of behavioural test in one study a more holistic understanding of the stress effects. For instance, using mirror-biting test and NTT, exposure to aggressive adult during juvenile phase in zebrafish shown to decrease aggressive behaviour later in adult phase without changing the anxiety level or locomotor activity ( Menezes et al, 2020 ), suggesting previous stress experience might reduce the motivation for social interaction but does not cause anxiety-like behaviour. By using just two different types of tests, it may be ruled out that in the study the reduced aggression in adult zebrafish is not due to heighten anxiety level but may be caused by other factors.…”

“…Juvenile zebrafish that faced aggressive, alcohol-influenced male adults displayed low levels of aggression towards their own reflections ( Menezes et al, 2020 ). Stressed adult male zebrafish, in the form of ‘losers’ in staged fights, are likely to lose their subsequent fights, indicating lower motivation, while the ‘winner’ fish are more likely to win their next fights ( Oliveira et al, 2011 ; Nakajo et al, 2020 ).…”

“…Exposure to an aggressive adult resulted in juvenile zebrafish to form tighter shoals with low average interindividual distances compared to naïve, unexposed controls ( Menezes et al, 2020 ). Both isolation and overcrowding resulted in loose cohesion within adult zebrafish shoals, with observations of greater distance between neighbours, indicating lower sociability after these two forms of social stress ( Saszik and Smith, 2018 ).…”